Apparatus and method for compensating for IQ mismatch in mobile communication system

Abstract

An apparatus and a method for increasing Error Vector Magnitude (EVM) performance representing quality of transmission signal are provided. The apparatus and the method suppress an image frequency component generated due to mismatch of IQ channels in order to transmit/receive a large amount of data without distortion in 4 th generation wireless communication standard candidate technologies such as a Long Term Evolution (LTE) system and a mobile WiMax system. The apparatus includes a LOcal frequency (LO) buffer including an amplifier. The LO buffer controls the gain and the phase of the amplifier using a control bit for controlling resistor connection.

The invention claimed is: 
     
       1. A transmitter for compensating for IQ imbalance in a mobile communication system, the transmitter comprising a LOcal frequency (LO) buffer for removing an image frequency component of an output terminal by controlling gains of an I-channel amplifier and a Q-channel amplifier,
 wherein the LO buffer removes the image frequency component of an I-channel by controlling a corresponding control bit until the image frequency component is removed, and then controls the control bit to remove the image frequency component by controlling a control bit of the Q-channel amplifier to remove a corresponding image frequency component. 
 
     
     
       2. The transmitter of  claim 1 , wherein the LO buffer controls gains of the I-channel amplifier and the Q-channel amplifier to remove the image frequency component of the output terminal by controlling a control bit for controlling a gain of the amplifier to remove an image frequency component, and storing information of the control bit that has removed the image frequency component. 
     
     
       3. The transmitter of  claim 1 , wherein each of the I-channel amplifier and the Q-channel amplifier comprises three amplification stages, and a last amplification stage of the three amplification stages comprises a variable resistor to control a gain using the control bit. 
     
     
       4. The transmitter of  claim 2 , wherein the control bit comprises a value defining resistor connection in order to control a gain of the amplifier. 
     
     
       5. A method for compensating for IQ imbalance in a mobile communication system, the method comprising removing an image frequency component of an output terminal by controlling gains of an I-channel amplifier and a Q-channel amplifier,
 wherein the removing of the image frequency component comprises:
 determining the image frequency component by controlling a control bit of an I-channel amplifier; 
 controlling the control bit until the image frequency component is removed; and 
 when the image frequency component of an I-channel is removed, controlling a control bit of the Q-channel amplifier to remove a corresponding image frequency component. 
 
 
     
     
       6. The method of  claim 5 , wherein the removing of the image frequency component further comprises:
 removing the image frequency component by controlling a control bit for controlling the gain of the amplifier; and 
 storing information of the control bit that has removed the image frequency component. 
 
     
     
       7. The method of  claim 5 , wherein each of the I-channel amplifier and the Q-channel amplifier comprises three amplification stages, and a last amplification stage of the three amplification stages comprises a variable resistor to control a gain using the control bit. 
     
     
       8. The method of  claim 6 , wherein the control bit comprises a value defining resistor connection in order to control a gain of the amplifier.